Driven by a desire to find new structural polysaccharides using enzymatic syntheses or genetic engineering of microorganisms, researchers have discovered polysaccharides that are biodegradable and can be made economically from renewably sourced feedstocks. One such polysaccharide is poly alpha-1,3-glucan, a glucan polymer characterized by having alpha-1,3-glycosidic linkages.
Poly alpha-1,3-glucan has been isolated by contacting an aqueous solution of sucrose with a glucosyltransferase (gtf) enzyme isolated from Streptococcus salivarius (Simpson et al., Microbiology 141:1451-1460, 1995). U.S. Pat. No. 7,000,000 disclosed the preparation of a polysaccharide fiber using an S. salivarius gtfJ enzyme. At least 50% of the hexose units within the polymer of this fiber were linked via alpha-1,3-glycosidic linkages. The disclosed polymer formed a liquid crystalline solution when it was dissolved above a critical concentration in a solvent or in a mixture comprising a solvent. From this solution continuous, strong, cotton-like fibers, highly suitable for use in textiles, were spun and used.
Development of new glucan polysaccharides and derivatives thereof is desirable given their potential utility in various applications. It is also desirable to identify glucosyltransferase enzymes that can synthesize new glucan polysaccharides, especially those with mixed glycosidic linkages and high molecular weight.